When fighting a moving aerial target using unguided projectiles fired from guns, the projectiles must be fired at the points where the aerial target will be located when the projectiles hit. Such points, normally called points of aim, must be predicted. A prediction, in this context, is an approximation of the aerial target's position a short time into the future. The approximation is based on knowledge of the aerial target's previous positions and a hypothesis of how the aerial target will behave in the future.
An approximation of the aerial target's current position and motion status based on a continuous data flow from an ongoing measurement of the aerial target's position is called an estimation of target data.
Estimation and prediction take place in parallel, at least until a fight sequence starts. At least one sensor is used to track and measure the aerial target's position. Based on measurement data from this sensor, the aerial target's current position and velocity are estimated. A predictor then calculates, based on estimate and hypothesis, how the firing weapons should be aimed.
Examples of the method and apparatus for fire control against aircraft are provided in patent document EP0527715 A1. There, the proposed prediction hypothesis is that an aircraft's trajectory can be described using one of a number of simple geometric models. No account is taken of the fact that the trajectory of an attacking, guided airborne weapon craft is a consequence of the guidance law applied by the airborne weapon craft to reach its target: in this case, hitting one of the objects of protection that the gun-based anti-aircraft defence is intended to defend.
The problem of currently existing solutions according to the above-mentioned document is thus that an attacking airborne weapon craft steering towards its target will, in general, not travel along a trajectory that can be described by a simple geometric model. Points of aim predicted based on an incorrect hypothesis regarding the future path of the aerial target will, of course, also be incorrect.
Further problems meant to be solved by the present invention will become apparent in connection with the following detailed description of the various embodiments.